<template>
    <transition name="viewer-fade">
        <div tabindex="-1" ref="lcy-image-viewer__wrapper" class="lcy-image-viewer__wrapper" :style="{ 'z-index': zIndex }">
            <div @click="onClickMask" class="lcy-image-viewer__mask"></div>
            <!-- CLOSE -->
            <span class="lcy-image-viewer__btn lcy-image-viewer__close" @click="hide">
                <i class="imageviewer iv-circle-close"></i>
            </span>
            <!-- ARROW -->
            <template v-if="!isSingle">
                <span class="lcy-image-viewer__btn lcy-image-viewer__prev" :class="{ 'is-disabled': !infinite && isFirst }" @click="prev">
                    <i class="imageviewer iv-arrow-left" />
                </span>
                <span class="lcy-image-viewer__btn lcy-image-viewer__next" :class="{ 'is-disabled': !infinite && isLast }" @click="next">
                    <i class="imageviewer iv-arrow-right" />
                </span>
            </template>
            <!-- ACTIONS -->
            <div class="lcy-image-viewer__btn lcy-image-viewer__actions">
                <div class="lcy-image-viewer__actions__inner">
                    <i class="imageviewer iv-zoom-out" @click="handleActions('zoomOut')"></i>
                    <i class="imageviewer iv-zoom-in" @click="handleActions('zoomIn')"></i>
                    <i class="lcy-image-viewer__actions__divider"></i>
                    <i :class="mode.icon" @click="toggleMode"></i>
                    <i class="lcy-image-viewer__actions__divider"></i>
                    <i class="imageviewer iv-refresh-left" @click="handleActions('anticlocelise')"></i>
                    <i class="imageviewer iv-refresh-right" @click="handleActions('clocelise')"></i>
                </div>
            </div>
            <!-- CANVAS -->
            <div class="lcy-image-viewer__canvas">
                <template v-for="(url, i) in urlList">
                    <img
                        v-if="i === index"
                        ref="img"
                        class="lcy-image-viewer__img"
                        :key="url"
                        :src="currentImg"
                        :style="imgStyle"
                        @load="handleImgLoad"
                        @error="handleImgError"
                        @mousedown.stop="handleMouseDown"
                    />
                </template>
            </div>
        </div>
    </transition>
</template>

<script>
import { on, off, rafThrottle, isFirefox } from './utils/util'
const Mode = {
    CONTAIN: {
        name: 'contain',
        icon: 'imageviewer iv-full-screen'
    },
    ORIGINAL: {
        name: 'original',
        icon: 'imageviewer iv-c-scale-to-original'
    }
}
const mousewheelEventName = isFirefox() ? 'DOMMouseScroll' : 'mousewheel'
export default {
    name: 'imageViewer',
    props: {
        urlList: {
            type: Array,
            default: () => []
        },
        zIndex: {
            type: Number,
            default: 2000
        },
        onSwitch: {
            type: Function,
            default: () => {}
        },
        onClose: {
            type: Function,
            default: () => {}
        },
        initialIndex: {
            type: Number,
            default: 0
        },
        closeOnClickMask: {
            type: Boolean,
            default: false
        }
    },
    data() {
        return {
            index: this.initialIndex,
            isShow: false,
            infinite: true,
            loading: false,
            mode: Mode.CONTAIN,
            transform: {
                scale: 1,
                deg: 0,
                offsetX: 0,
                offsetY: 0,
                enableTransition: false
            }
        }
    },
    computed: {
        isSingle() {
            return this.urlList.length <= 1
        },
        isFirst() {
            return this.index === 0
        },
        isLast() {
            return this.index === this.urlList.length - 1
        },
        currentImg() {
            return this.urlList[this.index]
        },
        imgStyle() {
            const { scale, deg, offsetX, offsetY, enableTransition } = this.transform
            const style = {
                transform: `scale(${scale}) rotate(${deg}deg)`,
                transition: enableTransition ? 'transform .3s' : '',
                'margin-left': `${offsetX}px`,
                'margin-top': `${offsetY}px`
            }
            if (this.mode === Mode.CONTAIN) {
                style.maxWidth = style.maxHeight = '100%'
            }
            return style
        }
    },
    watch: {
        index: {
            handler: function (val) {
                this.reset()
                this.onSwitch(val)
            }
        },
        currentImg(val) {
            this.$nextTick((_) => {
                const $img = this.$refs.img[0]
                if (!$img.complete) {
                    this.loading = true
                }
            })
        }
    },
    methods: {
        onClickMask() {
            if (this.closeOnClickMask) {
                this.hide()
            }
        },
        hide() {
            this.deviceSupportUninstall()
            this.onClose()
        },
        deviceSupportInstall() {
            this._keyDownHandler = rafThrottle((e) => {
                const keyCode = e.keyCode
                switch (keyCode) {
                    // ESC
                    case 27:
                        this.hide()
                        break
                    // SPACE
                    case 32:
                        this.toggleMode()
                        break
                    // LEFT_ARROW
                    case 37:
                        this.prev()
                        break
                    // UP_ARROW
                    case 38:
                        this.handleActions('zoomIn')
                        break
                    // RIGHT_ARROW
                    case 39:
                        this.next()
                        break
                    // DOWN_ARROW
                    case 40:
                        this.handleActions('zoomOut')
                        break
                }
            })
            this._mouseWheelHandler = rafThrottle((e) => {
                const delta = e.wheelDelta ? e.wheelDelta : -e.detail
                if (delta > 0) {
                    this.handleActions('zoomIn', {
                        zoomRate: 0.015,
                        enableTransition: false
                    })
                } else {
                    this.handleActions('zoomOut', {
                        zoomRate: 0.015,
                        enableTransition: false
                    })
                }
            })
            on(document, 'keydown', this._keyDownHandler)
            on(document, mousewheelEventName, this._mouseWheelHandler)
        },
        deviceSupportUninstall() {
            off(document, 'keydown', this._keyDownHandler)
            off(document, mousewheelEventName, this._mouseWheelHandler)
            this._keyDownHandler = null
            this._mouseWheelHandler = null
        },
        handleImgLoad(e) {
            this.loading = false
        },
        handleImgError(e) {
            this.loading = false
            e.target.alt = '加载失败'
        },
        handleMouseDown(e) {
            if (this.loading || e.button !== 0) return
            const { offsetX, offsetY } = this.transform
            const startX = e.pageX
            const startY = e.pageY
            this._dragHandler = rafThrottle((ev) => {
                this.transform.offsetX = offsetX + ev.pageX - startX
                this.transform.offsetY = offsetY + ev.pageY - startY
            })
            on(document, 'mousemove', this._dragHandler)
            on(document, 'mouseup', (ev) => {
                off(document, 'mousemove', this._dragHandler)
            })
            e.preventDefault()
        },
        reset() {
            this.transform = {
                scale: 1,
                deg: 0,
                offsetX: 0,
                offsetY: 0,
                enableTransition: false
            }
        },
        toggleMode() {
            if (this.loading) return
            const modeNames = Object.keys(Mode)
            const modeValues = Object.values(Mode)
            const index = modeValues.indexOf(this.mode)
            const nextIndex = (index + 1) % modeNames.length
            this.mode = Mode[modeNames[nextIndex]]
            this.reset()
        },
        prev() {
            if (this.isFirst && !this.infinite) return
            const len = this.urlList.length
            this.index = (this.index - 1 + len) % len
        },
        next() {
            if (this.isLast && !this.infinite) return
            const len = this.urlList.length
            this.index = (this.index + 1) % len
        },
        handleActions(action, options = {}) {
            if (this.loading) return
            const { zoomRate, rotateDeg, enableTransition } = {
                zoomRate: 0.2,
                rotateDeg: 90,
                enableTransition: true,
                ...options
            }
            const { transform } = this
            switch (action) {
                case 'zoomOut':
                    if (transform.scale > 0.2) {
                        transform.scale = parseFloat((transform.scale - zoomRate).toFixed(3))
                    }
                    break
                case 'zoomIn':
                    transform.scale = parseFloat((transform.scale + zoomRate).toFixed(3))
                    break
                case 'clocelise':
                    transform.deg += rotateDeg
                    break
                case 'anticlocelise':
                    transform.deg -= rotateDeg
                    break
            }
            transform.enableTransition = enableTransition
        }
    },
    mounted() {
        this.deviceSupportInstall()
        // add tabindex then wrapper can be focusable via Javascript
        // focus wrapper so arrow key can't cause inner scroll behavior underneath
        this.$refs['lcy-image-viewer__wrapper'].focus()
    }
}
</script>